This invention relates to hand tools, and in particular the invention is concerned with a hand tool for projecting a reference beam and a level and/or plumb beam of visible light for precise alignment in the same tool.
For some time laser beams have been added to the conventional carpenter's level to provide a handy tool for projecting a level line and for extending an existing line. In the level application a carpenter's level has a collimated laser beam parallel to the reference surface. When a sprit level on the carpenter's level is leveled by the operator, the reference surface of the carpenter's level is made level and the beam is parallel to the reference surface. This manual leveling step requires the user's time, and its elimination would be a benefit.
In an important application, an existing line, a wall line, for example, is extended by pushing the tool's reference surface against the existing wall and marking the laser beam location. In a similar application, the extended path of a pipe or duct can be located by pushing the reference surface against the pipe or duct and observing the beam path. It is an objective of the invention to provide the benefits of these applications to the user in an instrument which can also generate a level beam despite small tilt of the instrument's housing. By combining a self-leveling feature with the reference line feature, the instrument is useful in a great number of construction and layout situations.
FIG. 1 shows a typical prior art carpenter's level 2 with a built-in laser which produces a beam 6 parallel to a reference surface 3. In use the reference surface is used to extend a line or the unit is leveled with a base or with shims until a sprit level 4 indicates level providing a level reference. This design allows the use of a penta prism accessory 8 to deviate an incoming beam 10 by precisely 90 degrees, producing an outgoing beam 12. The term "reference surface" as used herein to refer to beam projecting tools is meant to describe a linear surface, preferably elongated and accurately parallel to the laser beam produced by the instrument in non-self-leveling mode.
A compact laser instrument 13 with reference surfaces is described in U.S. Pat. No. 5,594,993 and pictured in FIG. 2. It does not have any self-leveling features.
Self-leveling laser beam projectors are in wide use today as a stand-alone tool as shown in FIG. 3, manufactured by LeveLite Technology of Mountain View, California and described in U.S. Pat. No. 5,524,352. A self-leveling laser without a reference surface is described in U.S. Pat. No. 4,852,265. This instrument can switch from a level to a plumb beam by mechanically moving two mirrors. It has no reference surface as that term is used here, because the beam does not remain parallel to any such surface.
Numerous self-leveling compensators are used in rotating lasers which generate a plane as in U.S. Pat. No. 4,221,483. These compensators operate in two axes. Construction laser instruments used primarily for pipe laying as in U.S. Pat. No. 4,043,679, level primarily in the horizontal plane. Both of these categories do not use a mechanical reference surface on the instrument.